Identify the least stable ion amongst the following:

Options

A. `Li^(-)`
B. `Be^(-)`
C. `B^(-)`
D. `C^(-)`

Explanation

To identify the least stable ion among the given options, we will analyze the electronic configurations of each ion step by step.

### Step-by-Step Solution:

1. **Identify the Atomic Numbers and Electronic Configurations:**
- **Lithium (Li)**: Atomic number = 3
- Electronic configuration: \(1s^2 2s^1\)
- **Lithium Ion (Li⁻)**:
- Adding one electron: \(1s^2 2s^2\)

- **Beryllium (Be)**: Atomic number = 4
- Electronic configuration: \(1s^2 2s^2\)
- **Beryllium Ion (Be⁻)**:
- Adding one electron: \(1s^2 2s^2 2p^1\)

- **Boron (B)**: Atomic number = 5
- Electronic configuration: \(1s^2 2s^2 2p^1\)
- **Boron Ion (B⁻)**:
- Adding one electron: \(1s^2 2s^2 2p^2\)

- **Carbon (C)**: Atomic number = 6
- Electronic configuration: \(1s^2 2s^2 2p^2\)
- **Carbon Ion (C⁻)**:
- Adding one electron: \(1s^2 2s^2 2p^3\)

2. **Assess Stability Based on Electronic Configuration:**
- **Li⁻**: \(1s^2 2s^2\) - This configuration is stable as it has a filled 2s subshell.
- **Be⁻**: \(1s^2 2s^2 2p^1\) - This configuration is less stable because it has an unfilled p subshell (2p has one electron).
- **B⁻**: \(1s^2 2s^2 2p^2\) - This configuration is also less stable but more stable than Be⁻ as it has two electrons in the p subshell.
- **C⁻**: \(1s^2 2s^2 2p^3\) - This configuration is stable as it has a half-filled p subshell, which is generally more stable.

3. **Conclusion:**
- Among the ions analyzed, **Be⁻** is the least stable ion because it has an unfilled p subshell and is derived from a stable neutral atom (Be) to an unstable anion.

### Final Answer:
The least stable ion among the given options is **Be⁻**.